The present invention relates to a liquid crystal display module and, more particularly, to a field effect type liquid crystal display module having excellent time sharing drive characteristics and the capability of using monochromatic and multi-color displays.
In a liquid crystal display module of the "twisted nematic type", there is formed between two electrode substrates a helical structure which is twisted by 90 degrees by a nematic liquid crystal having a positive dielectric anisotropy, and polarizing plates are so arranged on the outer sides of the two electrode substrates that their polarizing axes (or absorbing axes) are perpendicular to or in parallel with the liquid crystal molecules adjacent to the electrode substrates (as disclosed in Japanese Patent Publication No. 13666/1976).
In this liquid crystal display element having an angle of twist (.alpha.) of 90 degrees, a problem arises not only in the steepness (.gamma.) of the change in the transmittance of the liquid crystal layer with respect to the voltage applied to the liquid crystal layer, but also in the visual angle characteristics thereof. Thus, the time sharing number (corresponding to the number of scanning electrodes) is practically limited to 64. In order to obtain an improvement of the image quality and an increase in the amount of display data for the liquid crystal display element in recent years, however, there has been proposed a super twisted nematic (STN) module in which the angle of twist .alpha. of the liquid crystal molecules is made larger than 180 degrees. It has been discussed in Applied Physics Letter 45, No. 101,021, 1284 (entitled "A new, highly multiplexable liquidcrystal display" by T. J. Scheffer & J. Nehring) that the time sharing drive characteristics of such a module are improved so as to increase the time sharing number by making use of a birefringence effect in that STN. There has also been proposed a (Super-twisted Birefringence Effect) display module.
This kind of liquid crystal display module includes an upper frame having a display window; a liquid crystal display panel having a liquid crystal plate integrated with a driver substrate; a conductor assembly having an optical diffusion plate and a conductor plate; an intermediate frame equipped with a linear back light source on at least one side thereof; and a lower frame. The module is constructed by laminating the above-specified components in the recited order and by jointing and fixing the upper frame and the lower frame.
Moreover, the aforementioned upper frame and lower frames are made of thin iron sheets, and the entirety is tightly laminated by sandwiching suitable spacers or adhesive tapes, if necessary, between the above-specified individual components so that it may be fixedly integrated.
In the liquid crystal display module of the prior art, since the upper frame and the lower frame are made of thin iron sheets, the liquid crystal display module has the disadvantage that the overall module has its thickness and weight increased, thereby imposing limitations on the reduction of the thickness and weight for purpose of maintaining its rigidity, and in that the heat generated by the back light source is transferred locally to the liquid crystal display panel to invite display irregularity.